1. Field of the Invention
The present invention relates generally to a process for selectively removing metallic material from a metallized film and, in particular, to the removal of metallic material from a metallized polymeric film using a printing method such as flexographic printing. The film can be a reflective film (e.g., a retro-reflective film) or a holographic film that can be used, for example, in an identification device comprising a radio frequency (RF) transponder.
2. Background of the Technology
Retro-reflective materials can reflect and re-emit incident light in a direction that is parallel to that of the source of the incident light. In other words, retro-reflective materials reflect light directly back toward the source of the light. Such materials and devices are widely used in the areas of nighttime transportation and safety. For example, retro-reflective materials are used to identify highway lanes and road signs using the light emitted from vehicle headlights. Retro-reflective materials are also used for the production of car plates, decals and distinctives for all kinds of vehicles and for truck containers, tractors and other applications. Retro-reflective materials have a bright effect under direct light without disturbing human sight.
Holographic materials have also been used for identification purposes. Since holograms are all but impossible to counterfeit, they are being increasingly used on all types of identification, including driver's licenses, credit cards, bus passes, etc., to increase security.
Both retro-reflective and holographic materials typically contain a very high level of metal such as aluminum. Holograms, for example, are typically stamped from metal foils. It is known that metal blocks the transmission and reception of radio frequency (RF) signals because the RF signal is absorbed or distorted by the metal content in the material. As a result, the signal cannot be received by an antenna blocked by metal. Such a blocked signal cannot be used, for example, to activate a connected device. This same blocking effect can occur whether the device is positioned on top of or underneath the metallic material because the distortion and absorption of the RF signal will be affected in either case. Thus, there is a problem in the prior art with regard to using retro-reflective and holographic materials, as well as other materials containing metals, on the surface of devices for receiving RF signals.
It would be desirable to incorporate an RF transponder into an identification device comprising a retro-reflective material, a holographic image, or other material containing a metal. The RF transponder could be used for electronic identification.